Breeders should have a professionally trained staff and employ proper restraining equipment on the horses when necessary.

Photo: Anne M. Eberhardt/The Horse

Before you breed au naturel, consider these tips.

Despite the widespread success of artificial insemination (AI), natural mating--or "live cover"--continues to be a popular choice for many equine breeders. This is partly due to live cover requirements for breed registries such as The Jockey Club for Thoroughbreds, and partly a matter of practicality or preference. But whatever your reason for choosing live cover, the following 10 tips will be useful as you plan a breeding program.

1. Know the risks of live cover

The image of au naturel might seem serene, but live cover comes with a host of risks that you won't find with artificial insemination.

With live cover, the stallion's full ejaculate is introduced into the mare's uterus. This represents much greater volumes of semen than with AI, and it is often accompanied by bacteria such as Streptococcus zooepidemicus. According to Andrew McGladdery, BVMS, CertESM, MRCVS, veterinary surgeon at Rossdale & Partners in Newmarket, U.K., these bacteria usually present no challenges for healthy mares, but they can create problems in susceptible mares (those that have difficulty clearing fluid from the uterus, which can result in excessive inflammation). This can be even more problematic if the mare is bred more than once in a cycle.

Timing of the breeding is another concern, as busy stallions must be protected from overbreeding. Stallions should usually not mate more than three times a day, McGladdery says, to help prevent fatigue and reduced semen quality. So for many breeders, especially in the Thoroughbred market, that means the mare gets bred just once per cycle. "With AI you can usually inseminate (your mare) at the most appropriate time in her cycle," he says. "But with live cover, you may have to fit in with what's available."

Security is another important issue in live cover. The mare, the stallion, and the handlers are at serious risk of injury due to sudden uncontrolled, possibly aggressive behavior in either horse. Breeders should have a professionally trained staff and employ proper restraining equipment on the horses when necessary.

2. Know the pros and cons of different kinds of live cover

In-hand breeding--where the handlers control horses, usually in a breeding shed or barn--maximizes the number of mares that can be covered safely by a single stallion. The process is generally quick, efficient, and well-managed by the breeding shed staff. Mares are often twitched and maintained with a foreleg lifted. If a mare is particularly resistant she might be sedated, McGladdery says.

Pasture mating involves releasing mares--usually several at a time--into a pasture with a stallion, sometimes for a few days, sometimes for a whole season. Human intervention is limited in pasture mating, which can increase the likelihood of a horse being injured. Pasture mating is not possible for all stallions because some can be too aggressive with mares, according to McGladdery.

3. Know the fertility of both horses

Owners of susceptible and low-fertility mares should avoid using stallions that have known low fertility; this can help them minimize cover to just once per cycle and maximize chances of conception, says McGladdery. "If a stallion has good fertility, the mare can be mated 48 or even 72 hours before ovulating," he says. This gives her more time to clear her uterus prior to ovulation, and she won't have to be bred a second time if she hasn't ovulated within the first 24 hours.

Breeding to a low-fertility stallion, even using a healthy, fertile mare, often translates into more intensive veterinary care for the mare because the veterinarian must check carefully for signs of impending ovulation. "With the subfertile stallion you usually want to be sure (the mare has) ovulated sooner (within 12 hours of breeding)," says McGladdery.

However, the fertility of a live-cover stallion isn't always apparent, as semen quality is rarely evaluated, according to McGladdery. The best way to find out is to ask about per-cycle pregnancy rates (percentage of mares that conceive per estrus) in previously covered mares.

4. Consider less popular stallions

It's easy to say you want the best stallion for your mare, but that comes at a price--and not just to your pocketbook. "With a busy stallion (covering up to 200 mares/season), that stallion may or may not be available when you actually want to mate your mare," McGladdery says. The result is that you might have to skip a cycle or accept breeding her a little too early and hope the sperm survive until the mare ovulates. The stallion's libido and fertility also are at risk, as they might vary over the season from frequent cover. Finally, you might not get to breed the mare to your desired stallion at all, due to lack of availability.

"The stud (farm) will try to cover every mare when required, but ultimately they will decide the order," he says. You might argue that you're a good client or that your mare's a great match, but in the end, your mare is still one in a hundred vying for a chance with that stallion during her cycle.

Less popular stallions can provide more flexibility and sometimes better fertility, McGladdery says. Sons of popular stallions often are great choices, as they can transfer high-quality traits while offering the genetic diversity of a younger generation.

5. Consider "chemistry"

Stallions and mares show clear preferences in mates, both in the wild and in domestic settings, according to Dominik Burger, DVM, PhD, head of research and equine reproduction at the Swiss National Stud in Avenches, Switzerland. Several factors appear to affect this partner choice, but recent studies have shown that major histocompatibility complex (MHC) might play a crucial role. MHC is a group of proteins coded by a set of genes that are also involved in the immune system. The greater the genetic differences found in the MHC between a stallion and mare, the more they seem to like each other.

MHC might provide clues about compatibility that affect fertility between individuals, according to Burger. One hypothesis, he says, is that if horses aren't attracted to each other (due to similar MHC), they could be less efficient as a reproducing couple. What's more, their offspring might even be less viable because of their MHC homozygous status.

Furthermore, horses that lack affinity for one another might go into live cover with a negative and/or aggressive attitude. These problems could even continue into future breedings with other horses and develop into a pathological mental status requiring treatment or retraining, he adds.

However, as it isn't practical to introduce mares and stallions to each other regularly before breeding, breeders might one day be able to take advantage of genetic testing. By selecting mates with considerably different MHC characteristics, owners are more likely to choose partners that would "have chemistry" with their own horses.

6. Reduce stress

Any kind of breeding program can be stressful for the horses involved, but live cover adds another level of stress because of the physical presence and contact of the other horse. Young mares, especially high-energy former race fillies, are easily stressed by leaving home, separation from stablemates, traveling, frequent veterinary exams, and the mating process with an unknown stallion.

Likewise, stallions are at risk of stress if they have to cover a large number of mares or compete during the breeding season.

Studies have shown that stress can interfere with fertility, depending on the individual horse, according to Burger.

Eliminate as many stress factors as you can. Consider transporting young mares with stablemates, and bring them to the stud farm several days before breeding to get accustomed to their surroundings. Reduce a stallion's workload whenever feasible, and give him regular days off from breeding for rest.

7. Prepare the horses, physically and mentally

Preparation for the breeding season should start the previous fall; any chronic health issues or reproductive problems should be addressed at this time. "Get (horses') problems sorted out in autumn," says McGladdery, "so that when they come in to be covered in February or March, we're not dealing with existing problems that could have been resolved."

Artificial light can allow the breeding season to start as early as February. Managers should put mares under lights beginning in early December. After about eight weeks of 16 hours of light per day, the mares should start cycling again and the stallions' semen quality might improve, McGladdery says.

You'll also want to be sure your horses have had good general care, especially deworming, according to Burger. As has been shown in other species, parasites could interfere not only with fertility, but also with a mate's attraction to the other.

8. Reorganize your barn

According to new research, stallions lined up in neighboring stalls take on a ranking order similar to young bachelor stallions in the wild. Dominant stallions have higher testosterone levels than their inferior stall neighbors, so the inferior ones exhibit less stallionlike behavior and might have poorer semen quality, Burger says.

Mares, on the other hand, show better receptivity to breeding if they can spend more time with a stallion. "Preliminary research results in our center demonstrate that permanent stallion contact affected mares' sexual behavior and cervical opening at insemination, and it led to higher conception rates of up to 9% per cycle," says Burger.

One explanation for this is that mares housed with a stallion have higher levels of oxytocin, which improves uterine contractions, meaning they clear their uterus more effectively after mating. During breeding, semen can enter the uterus more easily because the cervix is opened significantly wider.

So a good solution could be to separating the stallions in your (sturdy, well-constructed) stallion barn by placing mares between them. And while you're at it, consider reorganizing your pastures, too. Turnout and socialization can be important for good fertility, according to Burger.

9. Make sure the mare is really in heat

When it's time to cover, make sure your mare is really in heat to prevent frustration, save time and money, and protect people and horses from the vengeance of an unwilling mare.

Teaser stallions can reveal when a mare is receptive to mating and when she isn't. Protected by a half wall or bars, a stallion can be presented to a mare to "tease" her--check her reaction to his presence. If she turns her head, moves her tail to one side, lowers her croup (the area that extends from the loins to the tailhead), and urinates, she's in active heat and ready to breed. But if she squeals, lays back her ears, and tries to kick or bite, it's probably too soon--or too late.

Take teasing slowly, and let the mare have time to decide how to react, Burger says. Rushing the teasing process is bad management. Also, if possible, tease the mare with the same stallion she will be bred to because you might find she's receptive to one stallion but not another.

According to McGladdery, good veterinary involvement can be of real assistance when it comes to detecting heat. Through regular examinations--every 24-48 hours--veterinarians can check for the relaxed, pink cervix, the uterine edema, and the developing ovarian follicles that are the telltale signs of estrus. Even if the mare is not receptive to a teaser stallion, she could still conceive if bred according to these veterinary evaluations, he says.

10. Imitate nature

Breeding practices are continually evolving to accommodate what is natural to the horse. But this isn't just for the sense of having done a good deed: Horses in the wild have foaling rates reaching 95% compared to the 75% rate of domestic breeding, despite intensive veterinary involvement and research. "If nature has the best fertility rate, then we should be trying to copy that system as much as possible," says Burger.

Observations in the wild have revealed that feral stallions very typically mount a mare one or two times before finally mating her, although this is considered "poor behavior" in domestic stallions. "He might be just testing her to see if she'll kick," Burger says. "If we punish him for something that he considers to be normal, he might lose interest in breeding and develop libido problems."

He also suggests letting horses stay close to each other for a few minutes after mating rather than separating them immediately. It respects the social bond while allowing the stallion time to recover fully before standing on his own.

Take-Home Message

When working with live cover, getting a foal on the ground might be your primary goal, but safety and good behavior will make the experience--and future experiences--more positive. Keep in mind the physical nature of this kind of breeding, and you'll be off to a great start.

About the Author

Christa Lesté-Lasserre is a freelance writer based in France. A native of Dallas, Texas, Lesté-Lasserre grew up riding Quarter Horses, Appaloosas, and Shetland Ponies. She holds a master’s degree in English, specializing in creative writing, from the University of Mississippi in Oxford and earned a bachelor's in journalism and creative writing with a minor in sciences from Baylor University in Waco, Texas. She currently keeps her two Trakehners at home near Paris. Follow Lesté-Lasserre on Twitter @christalestelas.

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